The use of various thermoplastic resins to make fibers and fabrics is well known. In particular, propylene-based polymers and copolymers are well known in the art for their usefulness in a variety of applications, including the manufacture of staple fibers, which in turn are used to make yarn.
Propylene-based staple fibers are generally made using non-visbroken propylene polymers having a melt flow rate (MFR) of about 8-12 g/10 minute. However, use of such polymers can be costly due to additional processing equipment to transition from lower MFR grades. An alternative in the industry has been to visbreak low MFR propylene, such as propylene with a melt flow rate of about 4 g/10 minute during the staple fiber making process. However, visbreaking such polymers requires efforts to control the reactive extrusion process, costs associated with visbreaking agents, and reduced melt strength of the resultant fiber due to the visbreaking process.
Accordingly, there is a need for a propylene-based fiber composition having a target melt flow rate suitable for use as a staple fiber, without the need for visbreaking. Desirably, the composition has comparable spinability and tensile properties as compared to conventional staple fibers.